1. Field of the Invention
The present invention relates to a secret authentication system in which an authenticated apparatus notifies an authenticating apparatus of authentication data, so that authentication is performed while others are kept from knowing the data.
2. Description of Related Art
Systems providing a variety of services from a server to terminals connected via a network have rapidly been spreading recently, represented as Internet commerce systems, including Internet banking and Internet shopping. In the systems, which require an authentication system that verifies whether or not users are properly registered, authentication data, such as passwords, are transmitted on the network. Due to the nature of the systems, various technologies are known to prevent improper acts of making illicit gains through spoofing by using authentication data stolen from proper users (refer to Related Art 1, for example).
In addition, contactless IC cards functioning as electronic money have quickly been spreading recently. Contactless IC cards and RFID tags are getting used in entry control systems and merchandise control systems. In the systems of this type using RFID devices, it is necessary to prevent improper acts of making illicit gains through spoofing by using skimmed authentication data. Some schemes are known in order to increase security of the RFID devices, including a randomized hash lock scheme, a hash chain scheme (refer to Related Art 2), and a re-encryption scheme (refer to Related Art 3).    [Related Art 1] Japanese Patent Laid-open Publication No. 2007-293787    [Related Art 2] Japanese Patent Re-publication of PCT International Application No. 2005-031579    [Related Art 3] Japanese Patent Laid-open Publication No. 2004-317764
A variety of conventional technologies are able to increase secrecy of authentication data by employing complex calculation processes, but unable to sufficiently satisfy cost reduction demands since the technologies require high-speed computation devices that increase costs. It is thus desired to provide a technology capable of achieving both cost reduction and high secrecy. It is further desired in secret authentication systems to achieve a forward secure scheme, which prevents authentication information (authentication parties, authentication time and date, and the like) from being searched from the past; and a backward secure scheme, which prevents authentication information from being searched in the future.